This invention relates to chlorination or chlorosulfonation of olefin polymers. In particular, this invention relates to a process for preparation of chlorinated or chlorosulfonated olefin polymers in suspension in perfluorinated alkane, perfluorinated ether, or perfluorinated trialkyl amine media in the presence of fluorinated surfactants.
Chlorinated and chlorosulfonated olefin homopolymers and copolymers are well-known compositions useful as elastomers, coatings, adhesives, and inks. The chlorinated polymers are prepared on a commercial scale by reaction of chlorine with olefin polymers in either solution or aqueous suspension, while the chlorosulfonated analogues are prepared by reaction of olefin polymers with chlorine and sulfuryl chloride or sulfur dioxide in solution. Reactive extrusion and solventless processes have also been disclosed, for example in U.S. Pat. No. 3,347,835 and in U.S. Pat. No. 4,554,326. In addition, chlorination and chlorosulfonation of solvent-swollen ethylene polymers in fluids consisting of fluorocarbons having 1-4 carbon atoms has been disclosed in British Patent 1,325,579.
Each of these prior art processes has disadvantages. Specifically, solution processes require large volumes of organic solvents, generally chlorinated solvents such as carbon tetrachloride, which must be recovered and recycled. In addition, many chlorinated solvents are not inert to further chlorination. This leads to production of unwanted byproducts which must be removed. For example, hydrofluorocarbon solvents undergo appreciable chlorination resulting in the production of undesirable chlorofluorocarbons. In addition, due to the environmental hazards associated with these halogenated materials, stringent control of emissions and substantial investments in pollution control equipment are necessary. Aqueous suspension processes, on the other hand, cannot be used for preparation of chlorosulfonated olefin polymers. Further, chlorinations in aqueous suspension produce non-homogeneously chlorinated products. Reactive extrusion processes are not attractive because they are either limited to production of compositions containing low levels of chlorine, e.g. as disclosed in U.S. Pat. No. 4,554,326, or they are not adaptable for use on a commercial scale without major modification, see for example U.S. Pat. No. 3,347,835. Solventless processes are also not adapted to commercial scale exploitation. Finally, the process disclosed in British Patent 1,325,579, wherein fluorocarbon-swollen ethylene polymers are chlorinated or chlorosulfonated is unsuitable for preparation of a significant number of chlorinated ethylene copolymer resin types, in particular copolymers of vinyl acetate and methacrylic acid, because the surface tack of these polymers causes severe agglomeration during chlorination. In addition, these materials dissolve a portion of the chlorinated resin products resulting in sticky particle surfaces and necessitating additional isolation steps.
A slurry process which overcomes many of these disadvantages is disclosed in copending U.S. patent application Ser. No. 010,966, filed on Jan. 29, 1993 in the name of Edward Gus Brugel, entitled "Process for Chlorination and Chlorosulfonation of Olefin Polymers in the Presence of Fluorinated Surfactants", wherein the use of perfluorinated higher alkanes, perfluorinated ethers, and perfluorinated amines as reaction media for chlorination and chlorosulfonation of olefin polymers is described. Although this process eliminates use of undesirable chlorinated solvents, it too has its drawbacks. In particular, the process is not suitable for chlorination or chlorosulfonation of low molecular weight olefin polymers, i.e. those having weight average molecular weights below 10,000. Such polymers are tacky and tend to agglomerate which results in production of non-homogeneously chlorinated resins. In addition, in those cases wherein the chlorination is performed at temperatures above the softening temperature of the olefin polymers agglomeration often occurs.
It has now been found that polymer agglomeration can be substantially eliminated in chlorinations and chlorosulfonations conducted in perfluorinated liquid media if the processes are performed in the presence of fluorinated surfactants. This allows the slurry process to be extended to preparation of a broader spectrum of chlorinated and chlorosulfonated olefin polymers and permits more efficient production of these polymers under a wider range of reaction conditions than was formerly possible.